Urethane polymers or polyurethanes are a large family of polymers with widely varying properties and uses, all based on the reaction product of an organic isocyanate with compounds containing a hydroxyl group. Polyurethane polymers are generally classified into two broad categories: A. foam or urethane foam, and B. elastomers or polyurethane elastomers. Polyurethane foams are polyurethane polymers produced by the reaction of polyisocyanates with an hydroxyl group from a polyol and a polymerization catalyst, in the presence of water and/or an auxiliary blowing agent, such as monofluorotrichloromethane, which allows the polymeric mass to expand into a cellular mass upon reaction. In preparing a polyurethane elastomer, no blowing agent or mechanism for producing gas which would lead to cell development is present. Therefore, the polymer is produced by the reaction of the isocyanate with a hydroxyl group to form urethane linkages in the presence of a polymerization catalyst.
Polyurethane elastomers have been widely used in a variety of applications. They have been used as protective coatings, in the insulation of electrical elements, as caulks, sealants, gaskets, etc. Because of favorable rheology of an elastomer formulation, they can be used to cast intricate forms such as found in the toy industry. They have also been widely used in the preparation of sporting goods, fabric coatings and shoe soles wherein the cured urethane elastomer comes in repeated intimate contact with human beings. The prior art catalysts used to prepare elastomers frequently contained toxic mercury and lead compounds and the toxicity was carried over into the cured elastomer. If less toxic organotin compounds are employed as catalysts, elastomers having physical properties less than optimum are obtained.
There are several patents relating to various catalysts for reacting isocyanates with polyether polyols. U.S. Pat. No. 3,245,957 to Henderman et al describes a process for reacting an isocyanate with an active hydrogen compound in the presence of an antimony containing catalyst.
U.S. Pat. No. 3,203,932 to Frisch et al relates to a process for preparing urethane-urea elastomers using metal organic catalysts such as lead, cobalt and zinc napthenates.
U.S. Pat. No. 4,468,478 to Dexheimer et al discloses polyurethanes prepared from polyoxyalkylenes containing alkali metal or alkaline earth metal catalyst residues chelated with benzoic acid derivatives.
U.S. Pat. No. 3,714,077 to Cobbledick et al relates to a urethane foam catalyst system consisting of a combination of polyol-soluble organic stannous compounds with polyol-soluble organic bismuth and or antimony compounds with certain sterically hindered tertiary amines.